# Shared Flashcard Set

## Details

Astro 10 Final
Review for Astronomy 10 Sierra College Dunn
35
Astronomy
05/14/2011

Term
 Approximately, what basic composition are all stars born with? A) 90 percent hydrogen, 10 percent helium, no more than 1 percent heavier elements B) half hydrogen, half helium, no more than 2 percent heavier elements C) 98 percent hydrogen, 2 percent helium D) one-quarter hydrogen, three-quarters helium, no more than 2 percent heavier elements E) three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements
Definition
 E) three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements
Term
 Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ? A) luminosity they are formed with B) mass they are formed with C) time they are formed D) location where they are formed E) color they are formed wit
Definition
 B) mass they are formed with
Term
 A star's luminosity is the A) apparent brightness of the star in our sky. B) lifetime of the star. C) surface temperature of the star. D) total amount of light that the star radiates each second. E) total amount of light that the star will radiate over its entire lifetime.
Definition
 D) total amount of light that the star radiates each second.
Term
 Suppose that you measure the parallax angle for a particular star to be 0.5 arcsecond. The distance to this star is A) 2 parsecs. B) 5 parsecs. C) 0.5 light-year. D) 5 light-years. E) 0.5 parsec.
Definition
 A) 2 parsecs
Term
 The spectral sequence in order of decreasing temperature is A) ABFGKMO. B) OBAGFKM. C) OBAFGKM. D) BAGFKMO. E) OFBAGKM.
Definition
 C) OBAFGKM
Term
 Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram? A) surface temperature on the horizontal axis and luminosity on the vertical axis B) interior temperature on the horizontal axis and mass on the vertical axis C) mass on the horizontal axis and luminosity on the vertical axis D) surface temperature on the horizontal axis and radius on the vertical axis E) mass on the horizontal axis and stellar age on the vertical axis
Definition
 A) surface temperature on the horizontal axis and luminosity on the vertical axis
Term
 What is the smallest mass a newborn star can have? A) 800 times the mass of Jupiter B) about 1/80 the mass of our Sun C) 80 times the mass of Jupiter D) about 1/800 the mass of our Sun E) 8 times the mass of Jupiter
Definition
 C) 80 times the mass of Jupiter
Term
 What happens when a star exhausts its core hydrogen supply? A) Its core contracts, but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness. B) It contracts, becoming hotter and brighter. C) It contracts, becoming smaller and dimmer. D) Its core contracts, but its outer layers expand and the star becomes bigger and brighter. E) It expands, becoming bigger but dimmer.
Definition
 D) Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
Term
 Compared to the star it evolved from, a red giant is A) hotter and brighter. B) cooler and brighter. C) hotter and dimmer. D) the same temperature and brightness. E) cooler and dimmer.
Definition
 B) cooler and brighter.
Term
 What is a planetary nebula? A) a disk of gas surrounding a protostar that may form into planets B) the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star C) what is left of the planets around a star after a low-mass star has ended its life D) the expanding shell of gas that is left when a white dwarf explodes as a supernova E) the molecular cloud from which protostars form
Definition
 B) the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
Term
 Which of the following sequences correctly describes the stages of life for a low-mass star? A) red giant, protostar, main-sequence, white dwarf B) protostar, red giant, main-sequence, white dwarf C) protostar, main-sequence, white dwarf, red giant D) white dwarf, main-sequence, red giant, protostar E) protostar, main-sequence, red giant, white dwarf
Definition
 E) protostar, main-sequence, red giant, white dwarf
Term
 After a supernova event, what is left behind? A) always a neutron star B) either a white dwarf or a neutron star C) always a black hole D) always a white dwarf E) either a neutron star or a black hole
Definition
 E) either a neutron star or a black hole
Term
 White dwarfs are so called because A) it amplifies the contrast with red giants. B) they are the end-products of small, low-mass stars. C) they are both very hot and very small. D) they are supported by electron degeneracy pressure. E) they are the opposite of black holes.
Definition
 C) they are both very hot and very small.
Term
 How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf? A) It has a lower surface temperature. B) It has a larger radius. C) It has a smaller radius. D) It is supported by neutron, rather than electron, degeneracy pressure. E) It has a higher surface temperature.
Definition
 C) It has a smaller radius.
Term
 Which of the following is closest in size (radius) to a white dwarf? A) a basketball B) a small city C) a football stadium D) Earth E) the Sun
Definition
 D) Earth
Term
 Which of the following is closest in size (radius) to a neutron star? A) a city B) Earth C) the Sun D) a football stadium E) a basketball
Definition
 A) a city
Term
 From a theoretical standpoint, what is a pulsar? A) a binary system that happens to be aligned so that one star periodically eclipses the other B) a rapidly rotating neutron star C) a neutron star or black hole that happens to be in a binary system D) a star that alternately expands and contracts in size E) a star that is burning iron in its core
Definition
 B) a rapidly rotating neutron star
Term
 What is the basic definition of a black hole? A) a dead galactic nucleus that can only be viewed in infrared B) any object made from dark matter C) any object from which the escape velocity exceeds the speed of light D) any compact mass that emits no light E) a dead star that has faded from view
Definition
 C) any object from which the escape velocity exceeds the speed of light
Term
 Which of the following statements about black holes is not true? A) If you fell into a black hole, you would experience time to be running normally as you plunged rapidly across the event horizon. B) A black hole is truly a hole in spacetime, through which we could leave the observable universe. C) If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole. D) If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls nearer to the black hole. E) If you watch someone else fall into a black hole, you will never see him or her cross the event horizon. However, he or she will fade from view as the light he or she emits (or reflects) becomes more and more redshifted.
Definition
 C) If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole.
Term
 If you were to come back to our Solar System in 6 billion years, what might you expect to find? A) a rapidly spinning pulsar B) a red giant star C) a black hole D) a white dwarf E) Everything will be pretty much the same as it is now.
Definition
 D) a white dwarf
Term
 What is the diameter of the disk of the Milky Way? A) 100,000 light-years B) 100 light-years C) 1,000 light-years D) 1,000,000 light-years E) 10,000 light-years
Definition
 A) 100,000 light-years
Term
 Which of the following comprise the oldest members of the Milky Way? A) the Sun and other solar mass stars B) Cepheid variables C) globular clusters D) O stars E) red giant stars in spiral arms
Definition
 C) globular clusters
Term
 Approximately how long does it take the Sun to orbit the Milky Way Galaxy? A) 2.3 million years B) 230 million years C) 23,000 years D) 230,000 years E) 23 billion years
Definition
 B) 230 million years
Term
 Which constellation lies in the direction toward the galactic center? A) Leo B) Taurus C) Orion D) Sagittarius E) the Big Dipper
Definition
 A) Leo
Term
 Compared to spiral galaxies, elliptical galaxies are A) always much smaller. B) redder and flattened. C) bluer and rounder. D) bluer and flattened. E) redder and rounder.
Definition
 E) redder and rounder.
Term
 The disk component of a spiral galaxy includes which of the following parts? A) globular clusters B) spiral arms C) bulge D) halo E) all of the above
Definition
 B) spiral arms
Term
 Why are Cepheid variables important? A) Cepheid variables are stars that vary in brightness because they harbor a black hole. B) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future. C) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as "standard candles" for distance measurements. D) Cepheids are a type of young galaxy that helps us understand how galaxies form
Definition
 C) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as "standard candles" for distance measurements.
Term
 What is Hubble's law? A) The recession velocity of a galaxy is directly proportional to its distance from us. B) The recession velocity of a galaxy is inversely proportional to its distance from us. C) The longer the time period between peaks in brightness, the greater the luminosity of the Cepheid variable star. D) The faster a spiral galaxy's rotation speed, the more luminous it is. E) The faster a spiral galaxy's rotation speed, the less luminous it is.
Definition
 A) The recession velocity of a galaxy is directly proportional to its distance from us.
Term
 Based on current estimates of the value of Hubble's constant, how old is the universe? A) between 12 and 16 billion years old B) between 16 and 20 billion years old C) between 8 and 12 billion years old D) between 20 and 40 billion years old E) between 4 and 6 billion years old
Definition
 A) between 12 and 16 billion years old
Term
 I observe a galaxy that is 100 million light-years away: what do I see? A) the light from the galaxy as it was 100 million years ago and it is redshifted B) the light from the galaxy as it is today, but it is redshifted C) the light from the galaxy as it is today, but it is blueshifted D) the light from the galaxy as it was 100 million years ago and it it blueshifted E) Nothing: the galaxy lies beyond the cosmological horizon.
Definition
 A) the light from the galaxy as it was 100 million years ago and it is redshifted
Term
 Why should galaxy collisions have been more common in the past than they are today? A) Galaxies were much bigger in the past since they had not contracted completely. B) Galaxies attracted each other more strongly in the past because they were more massive; they had not yet turned most of their mass into stars and light. C) Galaxies were closer together in the past because the universe was smaller. D) Galaxies were more active in the past and therefore would have collided with each other more frequently. E) Galaxy collisions shouldn't have been more common in the past than they are now.
Definition
 C) Galaxies were closer together in the past because the universe was smaller.
Term
 What is a quasar? A) a starlike object that actually represents a bright patch of gas in the Milky Way B) a specialized astronomical instrument for observing distant stars C) the extremely bright center of a distant galaxy, thought to be powered by a massive black hole D) a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster E) another name for very bright stars of spectral type O
Definition
 C) the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
Term
 What is meant by "dark energy"? A) the agent causing the universal expansion to accelerate B) the total energy in the Universe after the Big Bang but before the first stars C) highly energetic particles that are believed to constitute dark matter D) any unknown force that opposes gravity E) the energy associated with dark matter through E=mc2
Definition
 A) the agent causing the universal expansion to accelerate
Term
 What is the evidence for an accelerating universe? A) White-dwarf supernovae are slightly dimmer than expected for a coasting universe. B) The Andromeda Galaxy is moving away from the Milky Way at an ever-increasing speed. C) White-dwarf supernovae are the same brightness regardless of redshift. D) There is far more dark matter than visible matter in the universe. E) White-dwarf supernovae are slightly brighter than expected for a coasting universe.
Definition
 A) White-dwarf supernovae are slightly dimmer than expected for a coasting universe.
Term
 To date, physicists have investigated the behavior of matter and energy at temperatures as high as those that existed in the universe as far back as ________ after the Big Bang. A) 300,000 years B) 1 million years C) 10-10 second D) 300 years E) 3 minutes
Definition
 C) 10-10 second
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